A search is underway for the brother of former reality star Kristin Cavallari and the brother-in-law of Chicago Bears quarterback Jay Cutler.

Michael Cavallari, 30, of San Clemente went missing more than a week ago. His 2014 Honda Civic was found abandoned off Interstate 70 in Grand County, Utah on Nov. 27, according to a statement from the county sheriff's office.

The door was open, the engine running and his laptop and cellphone were still inside the vehicle. The airbag was also deployed.

Authorities are worried the San Clemente native might be lost in the Utah wilderness, battling the harsh elements.

"The temperatures on the night of the incident were in the mid- to low-20s, very, very hostile conditions for somebody that was not properly equipped to be here," Grand County Sheriff Steven White said.

Credit card transaction receipts led authorities to a convenience store in Monticello, Utah, where Michael Cavallari was seen in footage on the store's security system.

Grand County is about 100 miles north of Monticello and 225 miles south of Salt Lake City.

Kristin Cavallari starred in the MTV reality series "Laguna Beach" as a teenager and then joined its spinoff "The Hills" when Lauren Conrad left the show.

Anyone with information on Michael Cavallari's whereabouts was urged to contact the Grand County Sheriff's Office at (435) 259-8115.